rmcg.dev/projects/FrontendMentor/newbie/product-preview-card-component/css/style.css

/*
 * design sizing
 *  Desktop: 1440x800
 *  Mobile: 375x667
 */

*,
::before,
::after {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

:root {
    /* Colors */
    /*I know style guide says dark cyan, but come on its dark green) */
    --col-primary-dark-green: hsl(158, 36%, 37%);
    --col-primary-darker-green: #1a4032;
    --col-primary-cream: hsl(30, 38%, 92%);

    --col-neutral-very-dark-blue: hsl(212, 21%, 14%);
    --col-neutral-dark-grayish-blue: hsl(228, 12%, 48%);
    --col-neutral-white: hsl(0, 0%, 100%);

    --col-page-background: var(--col-primary-cream);
    --col-card-background: var(--col-neutral-white);
    --col-button-text: var(--col-neutral-white);
    --col-button-background: var(--col-primary-dark-green);
    --col-button-background-hover: var(--col-primary-darker-green);
    --col-product-name: var(--col-neutral-very-dark-blue);
    --col-product-description: var(--col-neutral-dark-grayish-blue);
    --col-category-name: var(--col-neutral-dark-grayish-blue);
    --col-price-current: var(--col-primary-dark-green);
    --col-price-old: var(--col-neutral-dark-grayish-blue);

    /* Typography */
    --ff-category: "Montserrat", sans-serif;
    --ff-product-name: "Fraunces", serif;
    --ff-product-description: "Montserrat", sans-serif;
    --ff-price-current: "Fraunces", serif;
    --ff-price-old: "Montserrat", sans-serif;
    --ff-button: "Montserrat", sans-serif;

    --fs-category-name: 0.75rem;
    --lh-category-name: 0.9375rem;
    --ls-category-name: 5px;
    --fw-category-name: 500;

    --fs-product-name: 2rem;
    --lh-product-name: 2rem;
    --fw-product-name: 700;

    --fs-product-description: 0.875rem;
    --lh-product-description: 1.4375rem;
    --fw-product-description: 500;

    --fs-price-current: 2rem;
    --lh-price-current: 2rem;
    --fw-price-current: 700;

    --fs-price-old: 0.8125rem;
    --lh-price-old: 1.4375rem;
    --fw-price-old: 500;

    --fs-button: 0.875rem;
    --lh-button: 1.0625rem;
    --fw-button: 700;

    /* Styling */
    --border-radius-card: 0.625rem;
    --border-radius-button: 0.5rem;
    /* Positioning */
    --padding-product-details: 1.5rem;

    --width-product-card: 21.4375rem; /* 343px mobile */

    --margin-bottom-product-card__details: 1.5rem;
    --margin-bottom-product-card__category: 0.75rem;
    --margin-bottom-product-card__name: 1rem;
    --margin-bottom-product-card__description: 1.5rem;
    --margin-bottom-product-card__price-block: 1.25rem;

    /* Other */
    --img-desktop: url(images/image-product-desktop.jpg);
    --img-mobile: url(images/image-product-mobile.jpg);
    --image-filter: none;
}

body {
    min-height: 100vh;

    display: grid;
    place-content: center;

    background-color: var(--col-page-background);
}

.product-card {
    border-radius: var(--border-radius-card);
    background-color: var(--col-card-background);

    max-width: var(--width-product-card);
}
.product-card__image img {
    border-radius: var(--border-radius-card) var(--border-radius-card) 0 0;
    width: 100%;
    filter: var(--image-filter);
    /* filter: saturate(1.3); */
}
.product-card__details {
    padding: var(--padding-product-details);
}
.product-card__category {
    font-family: var(--ff-category);
    font-size: var(--fs-category-name);
    line-height: var(--lh-category-name);
    font-weight: var(--fw-category-name);
    letter-spacing: var(--ls-category-name);

    text-transform: uppercase;

    color: var(--col-category-name);

    margin-bottom: var(--margin-bottom-product-card__category);
}
.product-card__name {
    font-family: var(--ff-product-name);
    font-size: var(--fs-product-name);
    line-height: var(--lh-product-name);
    font-weight: var(--fw-product-name);

    color: var(--col-product-name);

    margin-bottom: var(--margin-bottom-product-card__name);
}
.product-card__description {
    font-family: var(--ff-product-description);
    font-size: var(--fs-product-description);
    line-height: var(--lh-product-description);
    font-weight: var(--fw-product-description);

    color: var(--col-product-description);

    margin-bottom: var(--margin-bottom-product-card__description);
}
.product-card__price-block {
    display: flex;
    gap: 1.1875rem;
    align-items: center;

    margin-bottom: var(--margin-bottom-product-card__price-block);
}
.product-card__price-current {
    font-family: var(--ff-price-current);
    font-size: var(--fs-price-current);
    line-height: var(--lh-price-current);
    font-weight: var(--fw-price-current);

    color: var(--col-price-current);
}
.product-card__price-old {
    font-family: var(--ff-price-old);
    font-size: var(--fs-price-old);
    line-height: var(--lh-price-old);
    font-weight: var(--fw-price-old);

    text-decoration: line-through;

    color: var(--col-price-old);
}
.product-card__button-buy {
    font-family: var(--ff-button);
    font-size: var(--fs-button);
    line-height: var(--lh-button);
    font-weight: var(--fw-button);

    color: var(--col-button-text);
    background-color: var(--col-button-background);

    border-radius: var(--border-radius-button);

    display: inline-flex;
    justify-content: center;
    gap: 0.75rem;

    outline: none;
    border: none;
    padding: 0.9375rem 0;
    width: 100%;
}

.product-card__button-buy:has(:focus, :hover) {
    background-color: var(--col-button-background-hover);
}

@media screen and (min-width: 1000px) {
    :root {
        --padding-product-details: 2rem 2rem 1.875rem 2rem;
        --width-product-card: 37.5rem;

        --margin-bottom-product-card__details: 0;
        --margin-bottom-product-card__category: 1.25rem;
        --margin-bottom-product-card__name: 1.5rem;
        --margin-bottom-product-card__description: 1.8125rem;
        --margin-bottom-product-card__description: 1.875rem;

        --margin-bottom-product-card__price-block: 1.8rem;
    }

    .product-card {
        display: flex;
    }

    .product-card__image img {
        border-radius: var(--border-radius-card) 0 0 var(--border-radius-card);
        width: 18.75rem;
        margin-bottom: unset;
        height: 100%;
    }

    .product-card__button-buy {
        padding: 0.9375rem 0;
    }
}

/* For Light / Dark button */

/* Update styling for checkbox */
html[data-theme="theme-dark"] {
    --col-light-yellow: rgb(201, 175, 103);
    --col-other-yellow: rgb(210, 169, 4);
    --col-page-background: var(--col-neutral-very-dark-blue);
    --col-card-background: rgb(97, 83, 83);
    --col-button-text: rgb(40, 4, 4);
    /* --col-button-background: rgb(48, 166, 48); */
    --col-button-background: rgb(48, 166, 48);

    --col-button-background-hover: rgba(7, 225, 7, 0.828);
    --col-product-name: var(--col-other-yellow);
    --col-product-description: var(--col-light-yellow);
    --col-category-name: var(--col-light-yellow);
    --col-price-current: var(--col-other-yellow);
    --col-price-old: var(--col-light-yellow);
    --image-filter: saturate(1.6);
}

.switch {
    position: absolute;
    display: inline-block;
    width: 40px;
    height: 40px;

    top: 10px;
    right: 10px;

    z-index: 30;
}

/* Hide default HTML checkbox */
.switch input {
    display: none;
}

.slider {
    position: absolute;
    cursor: pointer;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background-color: white;
    -webkit-transition: 0.4s;
    transition: 0.4s;
}

.slider:before {
    position: absolute;
    content: "";
    height: 40px;
    width: 40px;
    left: 0px;
    bottom: 4px;
    top: 0;
    bottom: 0;
    margin: auto 0;
    -webkit-transition: 0.4s;
    transition: 0.4s;
    box-shadow: 0 0px 15px #2020203d;
    background-image: url("../images/bs-moon-stars-fill.svg");
    background-repeat: no-repeat;
    background-position: center;
}

/* input:checked + .slider {
    background-color: #2196f3;
}

input:focus + .slider {
    box-shadow: 0 0 1px #2196f3;
} */

input:checked + .slider:before {
    color: green;
    background-image: url("../images/bs-sun-fill.svg");
    background-repeat: no-repeat;
    background-position: center;
}

.slider.round {
    border-radius: 34px;
}

.slider.round:before {
    border-radius: 50%;
}